1. Field of the Invention
The present invention relates to novel compositions for treating seeds as well as their production and uses.
2. Description of Related Art
The agricultural field produces crops of many varieties such as inter alia legumes, fruits, lettuce, wheat, barley, corn and rice. Many of these crops are grown from seeds that vary in their innate ability to resist physical damage due to unfavourable storage or environmental conditions, all of which affects their subsequent ability to grow into adult plants. Furthermore, seeds are susceptible to damage by plant pathogens including fungi, bacteria, viruses, and nematodes and are vulnerable to insects, birds, rodents, and other organisms that rely on them as a food source. Fungi are one of the most economically important groups of plant pathogens and are responsible for huge annual losses of marketable food, fibre and feed.
To reduce yield losses due to for instance fungal spoilage, a significant fraction of the seeds is currently treated with one or more synthetic agrochemicals. The use of synthetic agrochemicals to control plant pathogens, however, has increased costs to farmers and has caused harmful effects on the ecosystem. Consumers and government regulators alike are becoming increasingly concerned with the environmental hazards associated with the production and use of synthetic agrochemicals for protecting seeds from pathogens.
Furthermore, applying agrochemicals to the seeds themselves is fraught with problems such as bonding of the agrochemicals to the soil, agglomeration of the seeds due to the application of the agrochemicals and the use of expensive and complex chemical application equipment. In addition, seeds can be adversely affected by agrochemicals, as these chemicals can be toxic to the seeds and to the plants that sprout from the seeds. Such toxicity limits the amount of these agrochemicals that can safely be applied to the seeds. One undesirable effect of the toxicity is the reduction of the germination rate and/or speed, or even total lack of germination, of seeds that have been treated. Typically, the germination rate and/or speed of seeds that have been treated with an agrochemical that is toxic decreases with time after the chemical has been applied, thereby limiting the shelf life of the treated seeds. The toxicity of agrochemicals has been dealt with in several ways.
The inclusion of chemicals which ameliorate the toxic effects of agrochemicals along with the seeds is widely used. This solution however requires the application of an additional, often expensive, chemical component to the seeds.
Another way to overcome the toxic effect is to encapsulate the agrochemical in a matrix which limits its movement. This method can limit the contact of the agrochemical with the seeds and the emerging seedlings, while permitting the chemical to become available later during germination and initial plant growth as the chemical is released from the matrix. The proper operation of encapsulation technology depends on careful matching of the physical and chemical properties of the agrochemical and the encapsulating matrix. Neither one matrix, nor one encapsulation process, is suitable for encapsulation of all agrochemicals now in use for seed treatment. Moreover, the encapsulation matrix is susceptible to cracking.
Yet another way to overcome the toxic effect is to cover the seed with a relatively thick layer of inert material onto which the agrochemical is applied in such a way that it is not directly in contact with the seed (see WO 2004/049778). However, a disadvantage of this method is that at high dosage of agrochemical is necessary to be effective which still may lead to a possible toxic effect of the agrochemical for the seeds. Furthermore, due to the high dosage the coating's physiochemical properties may be changed significantly, indirectly producing a negative effect due to a change in the oxygen/water balance in the coating.
A further alternative includes the simultaneous sowing of seed-containing pellets and agrochemical-containing pellets as separate pellets (see US 2006/0150489). A disadvantage of this solution is that two separate pellets need to be made which is cumbersome and expensive. Moreover, this solution can stimulate irregular use of the agrochemical-containing pellets as there is no or only limited control at the application time, rate and location of the pellets.
Thus, there is a significant need for novel coating compositions for the control of seed pathogens that on the one hand possess a lower risk of pollution and environmental hazards than the currently used agrochemicals and that on the other hand are not toxic for the seeds.